Study: Genetically Engineered Corn Could Harm Aquatic Ecosystems

Oct 09, 2007

A study by an Indiana University (IU) environmental science
professor and several colleagues suggests a widely planted variety of
genetically engineered corn has the potential to harm aquatic
ecosystems. The study was published online on Oct. 8 by the journal Proceedings of the National Academies of Sciences.

Researchers, including Todd V. Royer, an assistant professor in the
IU School of Public and Environmental Affairs, found that pollen and
other plant parts containing toxins from genetically engineered Bt corn
are washing into streams near cornfields. They conducted laboratory
trials that found consumption of Bt corn byproducts produced increased
mortality and reduced growth in caddisflies, aquatic insects that are
related to the pests targeted by the toxin in Bt corn.

Caddisflies, Royer said, "are a food resource for higher organisms
like fish and amphibians. And, if our goal is to have healthy,
functioning ecosystems, we need to protect all the parts. Water
resources are something we depend on greatly."

Bt corn is engineered to include a gene from the micro-organism Bacillus thuringiensis,
which produces a toxin that protects the crop from pests, in particular
the European corn borer. It was licensed for use in 1996 and quickly
gained popularity. In 2006, around 35 percent of corn acreage planted
in the United States was genetically modified, according to the
researchers who cited U.S. Department of Agriculture data.

Before licensing Bt corn, EPA conducted trials to test its impact on water biota. But it used Daphnia, a crustacean commonly used for toxicity tests, and not insects that are more closely related to the target pests, Royer said.

The researcher emphasized that, if there are unintended consequences
of planting genetically engineered crops, farmers shouldn't be held
responsible. In a competitive agricultural economy, producers have to
use the best technologies they can get.

"Every new technology comes with some benefits and some risks,"
Royer said. "I think probably the risks associated with widespread
planting of Bt corn were not fully assessed."

Royer's research, conducted in 2005 and 2006 in an intensely farmed
region of northern Indiana, measured inputs of Bt corn pollen and corn
byproducts (such as leaves and cobs) in 12 headwater streams, using
litter traps to collect the materials. They also found corn pollen in
the guts of certain caddisflies, showing they were feeding on corn
pollen.

In laboratory trials, the researchers found caddisflies that were
fed leaves from Bt corn had growth rates that were less than half those
of caddisflies fed non-Bt corn litter. They also found that a different
type of caddisfly had significantly increased mortality rates when
exposed to Bt corn pollen at concentrations between two and three times
the maximum found in the test sites.

Royer said there was considerable variation in the amount of corn
pollen and byproducts found at study locations. And there is likely
significant geographical variation; farmers in Iowa and Illinois, for
example, are planting more Bt corn than those in Indiana. The level of
Bt corn pollen associated with increased mortality in caddisflies, he
said, "could potentially represent conditions in streams of the western
Corn Belt."

Other principal investigators for the study, titled "Toxins in
transgenic crop byproducts may affect headwater stream ecosystems,"
were Emma Rosi-Marshall of Loyola University Chicago, Jennifer Tank of
the University of Notre Dame and Matt Whiles of Southern Illinois
University. It was funded by the National Science Foundation.